In the course of the synthesis of some heterocyclic compounds, the reaction of the cyclic urea with carbon disulfide has been studied. The reaction of the cyclic urea with carbon disulfide gave two expected compounds, such as dithiocarbamic acid and bisdithiocarbamic acid2. However, from the reaction of the cyclic thiourea with carbon disulfide a variety of unexpected compounds have been isolated as crystals.
We wish now to report several unique compounds prepared from the reaction of ethylene thiourea with carbon disulfide and propose a reaction mechanism.
The following preparation of 2,2-bis(4',5'-dihydroimidazole-2'-thio)l,3-d.ithietane-4-spiro-211-imidazolidine (1) and Z-(4',5'-dibydroimidazole-2'-thio)-2-methylthio-1,3-dithietane-4-spiro-2~-~idazo~d~e (5) is representative.
The mixture of ethylene thiourea (1, 1 g, 9.8 mol), sodium hydride (50 % oil dispersion, 1.5 g, 31 mmol), dry THF (10 ml, distilled over CaH2), and diethyl carbonate (20 ml, dried over Zeolite) was stirred for 0.5 hr at 50-60ยฐC under N2 gas, To the reaction mixture was added dropwise a mixture of carbon disulfide (3 ml, 64 mmol) and HMPA (hexamethylphosphoric triamide, 5 ml, dried over Zeolite), The resulting mixture was stirred for 1 hr at room temperature and then poured into 100 ml of ice-water to afford a light yellow material. Recrystallization from pyridine gave 7 (0.75 g, 2.15 mmol, yield 66 %) as white prisms of mp 224-225~C~~~. The above filtrate was washed with benzene and then treated with a mixture of methyl iodide (2 ml) and ethanol (10 ml), The reaction mixture was kept to stand in refrigerator for 1 day to afford a light yellow material, Recrystallization from THF-H20 gave L1 (0.38 g, 1.29 mmol, yield 26 96) as light yellow plates of mp 195-1960C3*5.